In packaging and other operations, long, continuous chains of items such as labels and bags and other webs often have information such as the part number of a product being packaged printed directly thereon. Thermal imprinters are frequently utilized for such printing. Thermal imprinters operate by bringing the item to be printed into contact with a transfer material, such as foil, and applying heat with a print head at points of contact.
Problems associated with thermal imprinters include maintaining proper tension of the item being printed and maintaining the proper print area on each item. Additionally, movement of the foil between a supply reel and a take-up reel causes a static build-up due to the contact with the items. This problem is especially bad on cool and dry days and effects the electronics of the imprinter.
A proposed imprinter would have a paper sheet that is transported by a platen roller in conjunction with first and second pinch rollers. The pinch rollers would be positioned in parallel with a shaft of the platen roller on each side of the platen roller. The pinch rollers would be rotatably attached to respective pairs of substantially U-shaped arms that would be respectively mounted on each of two walls of a bracket. The arms would respectively be connected to the walls by springs so that the pinch rollers would urge the paper into contact with the surface of the platen roller. A pulse motor would selectively rotate its shaft in both clockwise and counterclockwise directions in accordance with supplied control signals. The platen roller would thereby cause the paper sheet to move in either a forward or backward direction. The pulse motor would receive signals which would cause the motor to drive the paper in either a forward or reverse direction as needed for printing.
Another proposed imprinter would utilize a microprocessor to compare the output of a paper take-up encoder with a stepper drive pulse count over a corresponding interval of time. The microprocessor would compare the output of the encoder and the drive pulse count to determine an indication of the current operating radius of paper wound upon a paper take-up reel. This comparison would be stored in a RAM. The microprocessor would then access a second function table stored in a ROM to determine the adjustment necessary in a take-up drive and thereby adjust the output torque of a take-up motor.